Large-Scale Edge Waves Generated by Hurricane Landfall

知识价值：飓风引起的沿海地区的浪涌和洪水是一个重要的社会问题。自由传播的波脉冲可能会在直接登陆区以外和登陆后几小时内造成严重的洪水。这些案件确实发生在过去。2005年10月24日，飓风威尔玛在佛罗里达西海岸登陆，对风暴潮的观测显示，威尔玛向内陆移动时形成了波脉冲，风暴潮不再受风力驱动。在测潮海平面资料中，波浪脉冲的高度超过1.5 m，但在涌浪资料中，由于波浪脉冲在低潮时传播，使其有些模糊。该波脉冲的持续时间约为6小时，传播速度在10-25 m s-1的范围内变化，表明初始扰动的演化过程。波脉冲被识别为具有大的空间和时间尺度的边缘波。飓风在大陆架上引起的这种持续时间相对较短的波浪以前没有报道。最有可能的是，它们逃脱了检测，因为NOAA和USGS维护的标准观测网络中的稀疏空间分辨率无法解决它们的相位传播。相反，以前的研究主要集中在低频海岸捕获波（CTW），其周期与惯性波相当或更长，被认为是热带气旋产生的主要波型。本计画将以过程导向的数值模拟方法，探讨飓风边缘波的产生与沿岸演变。更具体地说，以下问题将得到解决：-什么是最有利的条件，边缘波生成的飓风登陆？将描述飓风的大小、强度、移动速度和轨迹的作用，以及大陆架地形的作用。- 什么样的地形会引起边缘波的局部放大？大的地形变化的影响（加宽/缩小的大陆架、弯曲的海岸线等）和较小的特征（入口、河口、海角等）将进行系统研究。- 边缘波消散的机制是什么？耗散主要与底摩擦有关还是与离岸能量辐射有关？更广泛的影响：该项目的成果将在减轻危害、预防灾害和发展预警系统等领域应用于国家和区域安全。其结果对沿海区的管理和保护以及海洋作业也很重要。该项目将资助一名研究生。

Intellectual merit:The hurricane-induced surge and flooding in the coastal areas is an important societal problem. Severe flooding outside the immediate landfall area and a few hours after the landfall can be caused by a freely propagating wave pulse. The cases indeed occurred in the past. The observations of the storm surge induced by Hurricane Wilma landfall on the West Coast of Florida on October 24, 2005 revealed a formation of a wave pulse as Wilma moved inland and the surge was no longer sustained by the wind forcing. The height of the wave pulse exceeded 1.5 m in de-tided sea level data, but it was somewhat obscured in the surge measurements because of its propagating during the low tide. The duration of this wave pulse was ~6 hrs and the propagation speed varied within a range of 10-25 m s-1 indicating an evolution process of the initial disturbance. The wave pulse is identified as an edge wave with large spatial and temporal scales. Such relatively short-lasting waves induced by a hurricane on the continental shelf were not reported before. Most likely, they escaped detection, because a sparse spatial resolution in the standard observational network maintained by NOAA and USGS cannot resolve their phase propagation. Instead, the previous studies were focused on lower-frequency coastally trapped waves (CTW) with periods comparable to or longer than the inertial, which were thought to be prevailing wave modes generated by tropical cyclones. This project will investigate the generation and alongshore evolution of the hurricane-induced edge waves by means of process-oriented numerical modeling. More specifically, the following questions will be addressed: - What are the most favorable conditions for the edge wave generation by a hurricane landfall? The roles of the hurricane size, strength, translation speed and trajectory, as well as the role of shelf topography, will be delineated. - What topographic forms induce the local amplification of the edge waves? The effects of large topographic variations (widening/narrowing shelf, bending coastline, etc.) and smaller features (inlets, estuaries, capes, etc.) will systematically be studied. - What are the mechanisms of the edge wave dissipation? Is the dissipation mostly related with the bottom friction or with the offshore energy radiation? Broader impacts:The results of the project will have applications to national and regional security in such areas as hazard mitigation, disaster prevention, and the development of early warning systems. The results will also be important for coastal zone management and protection, as well as for maritime operations. One graduate student will be supported by this project.